When configuring BCS connections using SharePoint Designer, we can connect to three different data sources out-of-the-box:
You are, however, not limited to these data sources if you’re using the SharePoint API, which enables you to create your own custom connectors. Using the SharePoint API or object model to extend BCS connectivity is beyond the scope of this chapter. For further information on how to create custom BCS Connectors, see http://msdn.microsoft.com/en-us/library/ee554911.aspx.
The three main connection methods are discussed in the following sections.